Eye abnormalities in Joubert syndrome and related disorders.

Abstract

Abstract: : Purpose: Joubert syndrome is characterized by oculomotor abnormalities, truncal ataxia, hypotonia, developmental delay, and episodic hyperpnea and apnea. We report here the eye movement abnormalities and correlative magnetic resonance imaging (MRI) findings in 4 affected patients. Methods: Three children with Joubert syndrome and one with cerebello–oculo–renal syndrome were studied. All had quantitative recordings of gaze holding, and conjugate eye movements (saccades, smooth pursuit, full–field OKN, vertical axis VOR in the dark) using binocular video–oculography, and brain MRIs. Results: Gaze holding was uniformly unstable in primary and/or eccentric gaze. One child had seesaw nystagmus. Saccades were appropriately directed but mildly to severely dysmetric. Smooth pursuit gains during horizontal tracking of a sinusoidally modulated target (+/–10 deg) at peak velocity of 10,20 and 30deg/sec were consistently low, more so at higher stimulus velocities where tracking was primarily saccadic. High contrast, large field gratings (0.1c/d) drifted at 15,30 and 45 deg/s elicited OKN with gains at or below the lower limits of normal for age. Sinusoidal rotation about a vertical axis elicited VOR of high gain (near 1.0). All patients had hypoplasia of midline cerebellar structures. Conclusions: Patients with Joubert syndrome and related disorders have defects in gaze holding and severe abnormalities of conjugate eye movements that can be correlated with involvement of the oculomotor vermis and flocculus/paraflocculus. Whether these heterogeneous cerebellar disorders have unique oculomotor phenotypes is being studied.

Keywords: eye movements: conjugate • genetics • imaging/image analysis: clinical